package cn.iotab.iotkit.transport.api.common.util;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Base64;

/**
 * A simple utility class for Base64 encoding and decoding.
 *
 * <p>Adapts to Java 8's {@link java.util.Base64} in a convenience fashion.
 *
 * @author Juergen Hoeller
 * @author Gary Russell
 * @since 4.1
 * @see java.util.Base64
 */
public abstract class Base64Utils {

	private static final Charset DEFAULT_CHARSET = StandardCharsets.UTF_8;


	/**
	 * Base64-encode the given byte array.
	 * @param src the original byte array
	 * @return the encoded byte array
	 */
	public static byte[] encode(byte[] src) {
		if (src.length == 0) {
			return src;
		}
		return Base64.getEncoder().encode(src);
	}

	/**
	 * Base64-decode the given byte array.
	 * @param src the encoded byte array
	 * @return the original byte array
	 */
	public static byte[] decode(byte[] src) {
		if (src.length == 0) {
			return src;
		}
		return Base64.getDecoder().decode(src);
	}

	/**
	 * Base64-encode the given byte array using the RFC 4648
	 * "URL and Filename Safe Alphabet".
	 * @param src the original byte array
	 * @return the encoded byte array
	 * @since 4.2.4
	 */
	public static byte[] encodeUrlSafe(byte[] src) {
		if (src.length == 0) {
			return src;
		}
		return Base64.getUrlEncoder().encode(src);
	}

	/**
	 * Base64-decode the given byte array using the RFC 4648
	 * "URL and Filename Safe Alphabet".
	 * @param src the encoded byte array
	 * @return the original byte array
	 * @since 4.2.4
	 */
	public static byte[] decodeUrlSafe(byte[] src) {
		if (src.length == 0) {
			return src;
		}
		return Base64.getUrlDecoder().decode(src);
	}

	/**
	 * Base64-encode the given byte array to a String.
	 * @param src the original byte array
	 * @return the encoded byte array as a UTF-8 String
	 */
	public static String encodeToString(byte[] src) {
		if (src.length == 0) {
			return "";
		}
		return new String(encode(src), DEFAULT_CHARSET);
	}

	/**
	 * Base64-decode the given byte array from an UTF-8 String.
	 * @param src the encoded UTF-8 String
	 * @return the original byte array
	 */
	public static byte[] decodeFromString(String src) {
		if (src.isEmpty()) {
			return new byte[0];
		}
		return decode(src.getBytes(DEFAULT_CHARSET));
	}

	/**
	 * Base64-encode the given byte array to a String using the RFC 4648
	 * "URL and Filename Safe Alphabet".
	 * @param src the original byte array
	 * @return the encoded byte array as a UTF-8 String
	 */
	public static String encodeToUrlSafeString(byte[] src) {
		return new String(encodeUrlSafe(src), DEFAULT_CHARSET);
	}

	/**
	 * Base64-decode the given byte array from an UTF-8 String using the RFC 4648
	 * "URL and Filename Safe Alphabet".
	 * @param src the encoded UTF-8 String
	 * @return the original byte array
	 */
	public static byte[] decodeFromUrlSafeString(String src) {
		return decodeUrlSafe(src.getBytes(DEFAULT_CHARSET));
	}

}
